CDC 6600 - Why so awesome?

Swift Griggs swiftgriggs at
Tue Jun 21 16:06:02 CDT 2016

To my sorrow, I'd never heard of the CDC 6600 and I barely knew who 
Control Data was (whippersnapper, I know). I see a lot of traffic about 
them on the list and I went out to discover "why so cool?" Wikipedia and 
other spots talk about the features, but I'm trying to understand from 
folks who put hands to the metal, why they liked them so much.

I'm a total igmo concerning this bit of kit. Is this about right?

- It has dual "calligraphic" displays. Geeze! Very freakin' cool

- It was RISC nearly before folks could even articulate the concept

- It had some wicked cool "demos", to cop a C64 term. (ADC, PAC, EYE)

- It wasn't DEC and it wasn't IBM and it was faster than both when it hit 
  the street? 

- It has a cool OS? Dunno. Not much info on "SCOPE"

- Made in the USA baby! Back when we actually made things. 

- It used odd sized (by todays standards) register, instruction, and bus 
  sizes. 60 bit machine with 15/30 bit instructions. But, didn't it cause 
  a bunch of alignment issues for you ?

I dug into the CPU instructions for about 20 minutes and it was actually 
pretty straightforward. The so-called "COMPASS" ASM code was oh-so-cool. I 
can't believe they had so many of the features now considered "modern" or 
"clever" (at least by me) in the 1960s! This code:

... Is super-readable, in fact, probably a bit more than several 
much-newer dialects on different platforms. There was one instruction 
"PROTECT" I found pretty interesting, too. Was that similar to noodling 
with the control registers CR0, CR2, CR3, and CR4 on x86 to mark memory 
protection from segmentation violations? I remember that being the 
protection mechanism on my 386 SX/16 (and I remember it being a PITA), 
however the COMPASS "way" looks much easier/cooler and must have some 
hardware assistance to do that so easily.


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